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1.2.3 Implications – The EPR Paradox
Clearly, this exponential scaling of a quantum computer’s power with its number
of bits does not make immediate intuitive sense.
But thinking about the
implications of these two ideas – superpositions and entanglement – leads to far
more seemingly paradoxical scenarios. For example, if two quantum bits are put
into a superposition of the states 10 and 01, i.e. in a perfectly anti-correlated
state, a measurement of both qubits will always yield an opposite result for the
two bits, i.e. either a 0 and a 1 or a 1 and a 0. Quantum mechanics states that this
anti-correlation remains even if the two bits are separated and brought to opposite
ends of the universe. The apparent paradox arises from the fact that, even though
quantum mechanics tells us that both qubits will yield the opposite measurement
result with certainty, it states that it is impossible to predict which of the qubits
will yield a 0 and which one will yield a 1 since this choice is made only at the time
of measurement. Thus, as soon as one of the bits “decides” on its measurement
outcome, it needs to instantaneously inform the other bit about its decision no
matter how far away it is. As of today, though, this communication between the
bits is presumed impossible as it would have to happen at speeds faster than the
speed of light, which is currently believed to be the maximum speed at which anything,
even information, can travel. This paradox was first published by Einstein,
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